It is proposed to continue the research and development of radiopaque restorative and prosthetic dental resins. Acrylic resins capable of chelating salts of high atomic number elements have been developed during the duration of the program. Unlike the commonly used radiopaque resins consisting of heterogeneous physical mixtures of polymers and salts such as BaSO4, transparent materials of the required radiopacity level have been produced in which salts of barium, bismuth, zirconium, uranyl or other heavy metal salts interact with polymer-bound carbonyl, carboxylate, oligooxyethylene or phosphoryl ester moieties. The continuation proposal has the following specific aims: (1) develop better ambient curing systems; (2) investigate new monomer-salt systems, especially for obtaining materials with covalently bound anions; (3) develop resin systems with practical performance characteristics; (4) evaluate the performance properties of the radiopaque resins and (5) determine the scope of the chosen approach for synthesizing radiopaque resins. The methodology to achieve these aims include the synthesis and testing of new initiator-accelerator systems, the use of polymerizable heavy metal salts and chelating monomers to improve ion binding to the polymer matrix, and the application of a series of tests to evaluate the performance characteristics and properties of carefully selected formulations of radiopaque resins (e.g., radiopacity moldability, coalescence, working time, setting time, transparency, hardness, strength, leaching, storage stability, mutagenicity, toxicity). The project will continue as a collaborative effort between the Polymer Research Institute of the State University of New York (CESF in Syracuse, NY) and the Forsyth Dental Center in Boston, MA which is listed as a subcontractor in the budget request.